The present invention relates to a color display device.
Recently, color liquid crystal display devices are used in OA devices such as computers and displays of domestic electrified products such as televisions. As this type of color liquid crystal display device, there is widely known a color liquid display device of a TFT system. The color liquid crystal display device of a TFT system comprises color filters corresponding to three primary with thin film transistors (TFT), and a backlight having white color light sources. In this display device, liquid crystals corresponding to the respective color filters are made open by a drive circuit and light is transmitted through the liquid crystal made open, thereby obtaining a mosaic color mixture based on the combination of red, green and blue.
The above-described color liquid crystal display device of a TFT system enables the procurement of a clear full color image. However, on the other hand, the minute color filters of red, green and blue are needed for the respective pixel. Since the color filters are expensive parts in the color liquid display device.
Under the above-described circumstances, recently, there is proposed a color-filterless color liquid crystal display device which a three primary color backlight is combined with a monochromatic liquid crystal cell without the use of color filter and thin film transistor (see, for example, Japanese Patent Application Laid-Open Publication No. 6-138459). In this display device, pulse luminescence is caused of the three primary color light sources sequentially on a periodic basis, and the liquid crystal is made open with the same timing as that with which color light is given forth by such pulse luminescence to thereby green and blue.
Also, there is known a display device wherein three light guiding means are sequentially piled up, and any one of three primary color light sources is disposed in each of the light guiding means to thereby control the color distribution of each of the light sources through the on and off operation of respective switches, namely so-called electrically ornamented signboard.
However, in the above-described filterless color liquid crystal display device or electrically ornamented signboard, although many proposals concerning the control of the liquid crystal cell have hitherto bean made, there are not so many practical proposals concerning a backlight. For example, this type of backlight has three light sources. Therefore, miniaturization thereof is difficult. On the other hand, a color filter is provided on a light source side so as to obtain a pure color having a high degree of chromaticness. This raises the specific problem of being accompanied by an increase in the number of the parts used, with the result that the light utilization efficiency becomes inferior. No practical solution to this specific problem has hitherto existed.